1. Field of the Invention
The present invention is directed to an on-vehicle camera calibration device which is operated for calibrating the camera when it is mounted on a vehicle and/or when the current position of the camera mounted on the vehicle offsets from the criteria position and the present invention is also directed to a method of such a calibration and a calibration indicator used in such a method.
2. Prior Art
With respect to calibrating a camera, various companies and research organizations have been conducting research for establishing algorithms. As an example of such algorithms, a method is provided. In this method, a distinguishable 3D object having a known shape is placed as a calibration indicator in 3D space and depending on how the features of the 3D object are displayed in an image picked up by the camera for calculating the camera parameters. For example, such a method is disclosed in a paper titled xe2x80x9cINRIA Camera Calibration without Feature Extraction Research Reportxe2x80x9d No. 2204 (February 1994) pp. 1-21. In this disclosure, the camera parameters having a freedom degree of 11 are found by using the featured 3D calibration indicator.
Also, in Japanese Patent laid-open print No. Hei. 4-10344, an on-vehicle camera calibration device is disclosed. This device includes a camera which picks up a vehicular rear-view scene and a signal generator which generates an on-screen distance scale and/or characters. This device operates such that the distance scale is moved in the vertical direction at will within an on-screen image of the vehicular rear-view scene for placing the distance scale at a correct position on the screen.
In the former prior art, the camera parameters are determined from the 3D space in such a manner that the distinguishable 3D object having a known shape is placed at a position which can be picked up by the camera and an on-screen position of the 3D object in the camera image coordinate system is found on which the 3D object is placed. In this way, if the camera is calibrated after the camera is mounted on the vehicle, the calibration is made at the production or assembly line along which the vehicle is conveyed. In such a case, for doing the calibration successfully, the method of the calibration must be easy. On the shop-floor, if the calibration is made by using the characterized 3D object, it is not too efficient for the 3D object to be an indicator on the set point for each on-vehicle camera. In addition, placing the 3D object beneath the operator""s feet is not desirable from the view point of accident prevention and therefore is to be avoided. Thus, the calibrating indicator is desired to be one, such as an on-floor painted mark, which can be walked on by the operator.
On the other hand, in the latter prior art, the distance scale is moved in the vertical direction at will within the on-screen image of the vehicular rear-view scene for placing the distance scale at a correct position on the screen. In this method, setting the camera parameters is not accomplished, so that displaying the forecasted vehicle travel path at an arbitrary portion on the screen cannot be attained when the forecasted vehicle travel path which assists the driver""s steering operation during parking is desired to be displayed on the screen. Usual such a path is superposed on the image of the vehicular rear-view scene so as to be movable depending on the steering operation.
In view of the foregoing circumstances, the present invention provides (1) a camera calibration device and a method which make it possible to calibrate a camera even if the camera is mounted on a vehicle and (2) a calibrator indicator which makes it possible to set camera parameters for displaying an image on an arbitrary portion on the screen.
Thus, a need exists to provide, while maintaining the aforementioned advantage, a seat occupant sensor device in which the film is formed into a shape which increases in its the yield rate when punched from a resin sheet and which is capable of being equipped in various types of vehicular seats.
The present invention has been developed to satisfy the need noted above.
A first aspect of the present invention is to provide a camera calibration device for calibrating an on-vehicle camera based on an object placed in an image picked up by the on-vehicle camera, which comprises:
a planar calibration indicator as the object;
displaying means for displaying the image including the planer calibration indicator;
window displaying means for displaying an image on the displaying means;
adjusting means for adjusting a position of the window displaying means within a coordinate of the image picked up by the on-vehicle camera; and
parameter setting means for setting camera parameters such that when the calibration indicator comes within the window as a result of an adjustment by the adjusting means the resultant camera parameters are employed as the camera parameters.
In accordance with the first aspect, in the calibration, a planar calibration indicator is used and the camera image including the planar calibration indicator is displayed on the displaying means on which the window is also displayed. Within the image coordinate of the camera image the position of the window is moved and the position relation is adjusted by the adjusting means so that the planar calibration indicator falls in the window. When such a condition is established, the resultant camera parameters are used as the camera""s parameters to be set. This means that setting the camera""s parameters can be made only by manipulating the adjusting means. In this case, due to the fact that the calibration indicator is in the form of a planar configuration, when the calibration is fixed or adhered on the floor, the calibration is not disturbed and even in the vehicle production line the camera calibration can be made in easy fashion.
A second aspect of the present invention is to provide a camera calibration method of calibrating an on-vehicle camera based on an object placed in an image picked up by the on-vehicle camera, which comprises the steps of: preparing a planar calibration indicator as the object, displaying means for displaying the image including the planer calibration indicator, window displaying means for displaying a window on the displaying means, and adjusting means for adjusting a position of the window displaying means within a coordinate of the image picked up by the on-vehicle camera;
displaying the planar calibration indicator on the displaying means;
adjusting a position relation of the window so as to include the planar calibration indicator therein; and setting camera parameters such that the resultant camera parameters occur when the planar calibration indicator is located in the window.
In accordance with the second aspect, in the calibration the planar calibration indicator is used and the camera image including the planar calibration indicator is displayed on the displaying means on which also the window is displayed. Within the image coordinate of the camera image the position of the window is moved and the position relation is adjusted by the adjusting means so that the planar calibration indicator falls in the window. When such a condition is established, the resultant camera parameters are used as camera""s parameters to be set. This means that setting the camera""s parameters can be made only by manipulating the adjusting means. In this case, due to the fact that the calibration indicator in the form of a planar configuration, when the calibration is fixed or adhered on the floor, the calibration is not disturbed and even in the vehicle production line the camera calibration can be made in easy fashion.
In this case, if an adjustment is made by manipulating the adjusting means such that the on-screen is rotated or shifted relative to the calibration indicator, setting the camera parameters is made possible in an easy way, which makes it possible to display an image on an arbitrary portion on the screen. On the other hand, if the movable image related to the vehicular travel path is displayed in superposed fashion on the on-vehicle displaying means on which the picked-up scene image is displayed and a part of the movable image is used as camera parameters, no calibration indication is required to be placed in the 3D space picked up by the camera.
Moreover, as the movable image, a forecast vehicle travel path which varies with the steering angle is employed, obtaining camera parameters is made possible from a portion of the forecasted vehicle travel path, which makes it possible to confirm whether or not such a setting of the camera parameters is correct in an instant. In this case, the forecast vehicle travel path is displayed in the form of a ladder for indicating a distance as a span of two adjacent bars.
The entire disclosure of Japanese Patent Application H11-365754, upon which a claim for priority is based, is incorporated herein by reference.